From laboratory to the field: biological control of Fusarium graminearum on infected maize crop residues.

To evaluate biological control agents (BCAs) against Fusarium graminearum on infected maize stalks as a means to reduce Fusarium head blight (FHB) in subsequently grown wheat. In the laboratory, BCAs were applied against F. graminearum on maize stalk pieces. Clonostachys rosea inhibited the perithecia development and ascospore discharge when applied before, simultaneously with and after the pathogen. In the field, we simulated a system with high disease pressure, that is, a maize-wheat rotation under no-tillage, by preparing maize stalks inoculated with F. graminearum. The infected stalks were treated with formulations of C. rosea selected in vitro or the commercial BCA strain Trichoderma atrobrunneum ITEM908 and exposed to field conditions over winter and spring between winter wheat rows. Monitoring with spore traps and of FHB symptoms, as well as quantification of F. graminearum incidence and DNA in harvested grain revealed significant reductions by C. rosea by up to 85, 91, 69 and 95% compared with an inoculated but untreated positive control, respectively. Deoxynivalenol (DON) and zearalenone (ZEN) contents were reduced by up to 93 and 98%, respectively. Treatments with T. atrobrunneum were inconsistent, with significant reductions of DON and ZEN under warm and wet climatic conditions only. The findings support the application of C. rosea against F. graminearum on residues of maize to suppress the primary inoculum of FHB. As sustainable agriculture requires solutions to control FHB, hence, the application of C. rosea during the mulching of maize crop residues should be evaluated in on-farm experiments.